Bicarbonate Regulation of Aqueous Flow

碳酸氢盐对水流的调节

• 批准号: 8235350
• 负责人: ALAN D MARMORSTEIN
• 金额: $ 37.88万
• 依托单位: UNIVERSITY OF ARIZONA
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-04-01 至 2016-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8235350
• 关键词: Adenylate Cyclase; Adverse effects; Affect; American; Anions; Aqueous Humor; Bicarbonates; Blindness; Carbonic Anhydrase Inhibitors; Cells; Ciliary Body; Colon; Communication; Data; Drainage procedure; Drug usage; Endothelin; Endothelin-1; Epithelium; Exhibits; Eye; Gene Expression; Gene Proteins; Genes; Glaucoma; Goals; Goblet Cells; Knock-out; Laboratories; Lead; Mediating; Mouse Strains; Mus; Operative Surgical Procedures; Pathway interactions; Patients; Peptides; Permeability; Pharmaceutical Preparations; Phenotype; Physiologic Intraocular Pressure; Physiology; Pigment Epithelium; Play; Production; Protein Secretion; Proteins; Regulation; Resistance; Role; Testing; Therapeutic Intervention; Tissues; Transgenic Mice; United States; Vision; Visual impairment; Work; anterior chamber; aqueous; base; gamma-Aminobutyric Acid; inhibitor/antagonist; mouse model; novel; patch clamp; pressure; prevent; promoter; recombinase; role model; treatment strategy

DESCRIPTION (provided by applicant): Glaucoma is a leading cause of blindness in the United States affecting as many as 2.2 million Americans. All current glaucoma treatment strategies aim to reduce intraocular pressure (IOP). Recently our laboratory characterized a strain of mice with a targeted disruption of the Best2 gene, encoding the protein bestrophin-2 (Best2), an anion channel. In the eye, Best2 is expressed uniquely in the Non-Pigmented Epithelium (NPE) of the ciliary body. Best2-/- mice exhibit a significantly lower IOP than their wild type litermates. Surprisingly a comprehensive study of aqueous dynamics in these mice found that aqueous flow was increased and the reduced IOP observed in Best2-/- mice is due to a significantly diminished outflow resistance. Since Best2 is not expressed in outflow tissues, these effects must arise from direct communication between the inflow and outflow pathways via a pressure independent mechanism. An important goal of this application is to understand the basis of this communication. Bestrophins have a high permeability to bicarbonate, and we have recently shown that Best2 physiologically carries a bicarbonate conductance in colon goblet cells. Although carbonic anhydrase inhibitors have been used to lower IOP for many years, the role of bicarbonate in generating aqueous flow is unclear. Our preliminary data establish that a bicarbonate sensitive soluble adenylate cyclase (sAC), is expressed in NPE cells and that this sAC can regulate outflow. Yet, sAC like Best2 does not appear to be expressed in drainage tissues. Furthermore, endothelin-1 (ET1) levels are elevated in the aqueous humor of Best2-/- mice. ET1 has been shown to alter both inflow and outflow resistance potentially explaining the unusual phenotype of the Best2-/- mouse. Based on these data we propose to test the hypothesis that bicarbonate, carried by Best2 channels, is a central player in the regulation of inflow AND outflow, and that sAC mediates communication of the inflow and outflow pathways by regulating the secretion of soluble messengers such as endothelins into the aqueous humor. This will be tested in 3 specific aims. In aim 1 we determine whether bestrophin 2 serves as a bicarbonate channel in NPE cells. In aim 2, we determine the role of soluble adenylyl cyclase in the regulation of aqueous flow and intraocular pressure. In aim 3 we probe the role of bicarbonate in regulating secretion of bioactive peptides such as endothelin-1 by the ciliary body. At its conclusion this work will provide a comprehensive model of the role of bicarbonate in the physiology of the anterior chamber of the eye and could potentially lead us to new avenues for therapeutic intervention in glaucoma. PUBLIC HEALTH RELEVANCE: All current glaucoma treatments seek to reduce intraocular pressure. Deficency of the anion channel bestrophin 2 in mice results in a diminished intraocular pressure despite increased production of aqueous humor, implying the existence of a pressure independent mechanism for regulation of outflow. Understanding how bestrophin 2 functions in the cilliary epithelium and how bicarbonate regulates aqueous production and drainage will lead us to new therapies to prevent or cure vision loss due to glaucoma.

描述（由申请人提供）：青光眼是美国失明的主要原因，影响了多达220万美国人。当前的所有青光眼治疗策略旨在降低眼内压（IOP）。最近，我们的实验室表征了小鼠的菌株，其靶向破坏最佳2基因，编码蛋白质Bestrophin-2（Best2），一个阴离子通道。在眼中，Best2在睫状体的非色素上皮（NPE）中唯一表达。 Best2 - / - 小鼠的IOP明显低于它们的野生型litermates。令人惊讶的是，对这些小鼠的水性动力学的全面研究发现，水流增加，并且在Best2 - / - 小鼠中观察到的IOP降低是由于流出电阻显着降低。由于最佳2在流出组织中未表达，因此必须通过独立压力机制在流入和流出路径之间的直接通信产生这些效果。该应用程序的一个重要目标是了解这种交流的基础。 BestRophins对碳酸氢盐的渗透性很高，我们最近表明，Best2在生理上携带碳酸氢盐在结肠杯状细胞中具有碳酸氢盐电导。尽管碳酸酐酶抑制剂已用于降低IOP多年，但碳酸氢盐在产生水流中的作用尚不清楚。我们的初步数据表明，碳酸氢盐敏感的可溶性腺酸环化酶（SAC）在NPE细胞中表达，并且该SAC可以调节流出。但是，像Best2一样的SAC似乎在排水组织中没有表达。此外，在Best2 - / - 小鼠的水性幽默中，内皮素-1（ET1）水平升高。 ET1已被证明会改变流入和流出阻力，从而可能解释了最佳2 - / - 小鼠的异常表型。基于这些数据，我们建议测试以下假设：最佳2通道携带的碳酸氢盐是调节流入和流出的核心参与者，并且SAC通过调节诸如Endothelins等可溶性Messenger的分泌来调节流入和流出途径的通信。这将在3个特定目标中进行测试。在AIM 1中，我们确定Bestrophin 2是否用作NPE细胞中的碳酸氢盐通道。在AIM 2中，我们确定可溶性腺苷酸环化酶在调节水流和眼内压的调节中的作用。在AIM 3中，我们探测了碳酸氢盐在调节纤毛体的生物活性肽（例如内皮素-1）分泌中的作用。在其结论中，这项工作将为碳酸氢盐在眼前腔室生理学中的作用提供全面的模型，并有可能导致我们进入青光眼治疗干预的新途径。 公共卫生相关性：所有目前的青光眼治疗旨在降低眼内压力。阴离子通道在小鼠中BESTROPHIN 2的不足导致外部压力降低，尽管水性幽默的产生增加了，这意味着存在用于调节流出的压力独立机制。了解如何在cilliary上皮中发挥作用，以及碳酸氢盐如何调节水性生产和排水，将导致我们采取新的疗法，以预防或治愈因青光眼引起的视力丧失。